Lamp base



FIG. 1 is a top perspective view of the lamp base;

FIG. 2 is a side view thereof with all sides being the same;

FIG. 3 is a top view thereof; and,

FIG. 4 is a bottom view thereof.

The broken lines represent environment of use and form no part of the claim. 

The ornamental design for a lamp base, as shown and described. 